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Tiny lady beetles have big biocontrol
potential

Immigrants are among Americas greatest strengths, and this
holds true not just for people.

Many of our major food plants wheat, soybeans, rice,
potatoes, and othersoriginated outside North America. And so do many of
our beneficial insects.

Colonists from England brought in our most valuable and
well-known bee for making honey and pollinating crops, Apis mellifera.

Other six-legged immigrants include some species of lady beetles
that give farmers biological options to insecticides.

New information suggests that several non-native lady beetles
arrived in a time-honored immigrant fashionby boatsays Agricultural
Research Service entomologist William H. Day. But most non-native biocontrols
are here by invitation.

USDA scientists have gone overseas for more than 100 years
to search for, test, import, rear, release, and evaluate exotic beneficial lady
beetles, parasitic wasps, other insects, and microorganisms. It usually takes
several years for an imported beneficial organism to build up enough in number
to reduce pests, says Day, who is located at the ARS Beneficial Insects
Introduction Research Laboratory in Newark, Delaware.

Biocontrol species discovered and imported by ARS reduce damage
by many pests, such as gypsy moths and sugarcane borers, and weeds such as
water hyacinth.

Some successes have been dramatic, including substantial control
of at least five insect pests (cereal leaf beetle, Rhodesgrass mealybug, pea
aphid, alfalfa blotch leafminer, alfalfa weevil) and three weeds (Klamath weed,
alligatorweed, puncturevine). The agency has estimated that biocontrol of these
eight pests is worth over $250 million a year to farmers.

One modern spur to biocontrol efforts was the discovery, in the
1960s, that milk from some cows contained insecticide used against
alfalfa weevils. This accelerated anti-weevil biocontrol efforts already under
way by Day and colleagues.

In the 1960s and 1970s, the scientists released
about a dozen weevil biocontrols, mostly parasitic wasps. Roughly half the
insects became established. In New Jersey, in a pattern later repeated
elsewhere, the proportion of alfalfa growers spraying weevil insecticide
tumbled from 93 to 7 percent by the early 1970s.

Around 1980, USDAs Animal and Plant Health Inspection
Service (APHIS) began releasing the parasites nationally. Within a decade,
biocontrol was saving alfalfa growers $88 million a year.

Today, most biocontrol imports are parasites that spend part of
their life cycles inside a hostusually one or a few species of pests.
Predators, however, devour their prey directly, and most are less picky about
whats on the menu.

One of the most successful non-native predators is Coccinella
septempunctata, the sevenspotted lady beetle. Imported and released as
early as 1959, it now occurs throughout the United States, eating pea aphids,
apple aphids, cereal aphids, greenbugs, and other pests.

The seven-spot and five other exotic lady beetles
have made the Eastern United States their adoptive home since 1912, most since
the 1960s, Day says. The five are Propylea quatuordecimpunctata,
Coccinella undecimpunctata, Hippodamia variegata, Harmonia quadripunctata,
and H. axyridis.

Though scientists released some of these species, including the
seven-spot, Day says evidence indicates all six first became
established from insects that arrived on their own.

He drew this conclusion by comparing records of the
beetles first collections to prior releases, if any, in nearby counties
and states. He compiled and analyzed records gathered by cooperators with ARS,
APHIS, the New Jersey Department of Agriculture, and University of Connecticut
Cooperative Extension.

All six species were first found close to seaports or
shipping lanes near Quebec City, Montreal, Boston, New York City, or New
Orleans, he says, noting that none had previously been released in the
area where it was first discovered. The records show the insects
descendants fanned out from port areas, he says.

In the 1960s, says Day, P-14s probably jumped ship
in Canada along the St. Lawrence River. The first specimens turned up in 1968
near the city of Quebec, and then the insects dispersed southward.

But now, says Day, weve found P-14s in 86 new
counties and 6 new states just since 1988. Theyre in every New England
state and in New York, New Jersey, and Pennsylvania. This is encouraging for
farmers and gardeners who contend with aphids on fruits, vegetables, and other
crops. He and others have collected P-14s from an array of trees
and weedsas well as from alfalfa, broccoli, cabbages, sweet corn,
raspberries, blueberries, euonymus, tomatoes, vetch, and clover.

Several ships have likely departed for America with P-14s
aboard, he says. At least one band of these lady beetle colonists was hardy and
lucky enough to survive and reproduce. Day says their odds improved after 1959.
Thats when the St. Lawrence Seaway opened, linking the Atlantic to inland
ports as far as 2,000 miles west on Lake Superior.

Port inspections intercept pests trying to hitch a ride with
cargo. But insects that fly ashore from ships on inland waterways would escape
detection. Day says foreign-born lady beetles could find shelter in or on cargo
containers or shipboard structures with protective nooks and crannies.

And compared to urbanized coastal ports, lady beetles leaving a
ship on an inland channel would stand a better chance of finding aphids nearby
in farms and forests.

Factors that favored P-14s progress in the Northeast could
also help it gain a foothold in the West. There, scientists have released it,
but with little success so far, says David Prokrym of APHIS. He collaborated
with Day in analyzing the beetle collection records.

In Niles, Michigan, Prokrym coordinates APHIS biocontrol
project aimed at Russian wheat aphids. These leaf-sucking pests invaded around
1986. They now infest wheat and barley in 17 Great Plains and western states.
Growers annually pay a multimillion-dollar tab for aphid-related yield loss and
insecticides.

From 1987 to 1993, APHIS released 591,000 lab-reared P-14s
in 16 Western States. Surveys have not detected any established populations.

At first it seems perplexing, Prokrym says,
that P-14s established themselves naturally on the East Coast but
not in the West. On the other hand, New England isnt Texas.

The Northeast is more moist, has more plant and habitat
diversity, and has smaller farms than the Great Plains. There, wheat may span
the horizon. Or fields may be left fallow for a year after harvest, to conserve
soil moisture.

For future beetle releases, says Prokrym, we
are looking for sites near grain fields, where there is a steady water source
and the vegetation is more diverse and stable. An example would be a wildlife
management area having a pond and grain for waterfowl. Here, P-14s might
find the habitat and aphids to bridge the fallow period in commercial
wheatfields.

Some mystery shrouds H. axyridis, an Asian lady beetle
that now thrives in the United States. In recent years it has set up homes in
the East, South, and Northwest.

Day concludes, from collection records, that this beetle first
became established from ancestors that entered by ship at the ports of New
Orleans and Seattle.

The beetle apparently failed to adapt after releases in
California in 1916 and the mid-1960s, says entomologist Paul Schaefer at
ARS Newark lab. In the late 1970s, he collected about 700 H.
axyridis in Japan and shipped them to Newark. The lab supplied beetles to
other researchers, though chiefly to entomologist Louis Tedders at ARS
Southeastern Fruit and Tree Nut Research Laboratory in Byron, Georgia.

From 1978 to 1981, Tedders reared and released 88,000 H.
axyridis in a pecan orchard used for research at Byron. About that time,
others released the beetles in the South, East, and Northwest, but again they
seemed to vanish.

That summer, however, Louisiana State University scientists
found the first established U.S. populations in Abita Springs, Louisiana. It is
hundreds of miles from areas where H. axyridis had previously been
releasedbut only a few miles from New Orleans.

This lady beetle also is common in western Washington,
especially near Puget Sound, an inlet used by ships headed to the ports of
Seattle and Tacoma. But it wasnt seen until 1994 in the region of
Washington east of the Cascade Mountains, where ARS scientists released it in
1981 and 1982.

In 1990, many H. axyridis beetles were seen in Buchanan,
Georgia, about 110 miles north of Byron. We didnt recover any in
Byron until 1992, Tedders says. The Buchanan beetles probably
descended from those we released at Byron, but well never know.
Whats important to farmers is not how the beetles got here but what
theyre doing to aphid pests.

Where present, Tedders says, H.
axyridis has nearly eliminated pecan aphids. Some growers have tended to
spray instead of letting a natural control take its course. But now, I know a
lot of pecan growers who wouldnt even think of spraying.

Its too early to know the total influence of H.
axyridis on the pecan industry, but I believe its impact is among the most
important of any biocontrol during the last 30 years.

A biological standout in many ways, H. axyridis has a
wider range of colors and spot numbers than other lady beetles. Wings range
from black to mustard; spots number zero to many. The most common United States
form is mustard to red with 16 or more black spots. But the species is easy to
identify from its big false eyestwin white football-shaped
markings behind the head.

This lady beetle is also prolific: Adult beetles fed on pecan
aphids in Tedders laboratory laid about 20 eggs a day.

Barely one-quarter-inch long, the insect has a big appetite.
Even before reaching adulthood, one beetle can eat 300 aphids,
Schaefer says. Its dinner menu can include more than 50 species of aphids and
other soft-bodied insects that are pests of ornamental rose, crape myrtle,
plum, peach, apple, magnolia, clover, cabbage, vetch, pine, tulip tree, maple,
and other plants.

H. axyridis dwell mainly in trees. For several days
during autumn, however, they typically aggregate, or cluster, in large numbers
on sunny sides of light-colored rock outcrops or structures. Nearby crevices
may offer winter shelter from storms, cold, and wind.

But the insects occasionally aggregate on homes and other
buildings, especially those with light colors and sunny southwest exposures.
Sometimes, the ladybugs use openings such as uncaulked window frames to become
a crowd of uninvited guests.

This can certainly be a nuisance, but people
shouldnt be alarmed, says Schaefer.

He and Tedders advise people to avoid killing the ladybugs by
spraying them with an insecticide or squashing them. Handling ladybugs or
picking them off a wall causes a stress-related defensive behavior: they
secrete an orange substance that, though harmless, can stain walls and fabric.

This substance actually is ladybug blood, says
Tedders. It comes out the joints of the legs. The phenomenon is called
reflex bleeding, and all ladybugs do it when stressed. If you trap one in your
hand for several seconds, you may see a spot of beetle blood on your
palm.

Tedders and Schaefer suggest removing indoor aggregations with a
vacuum cleaner with a crevice tool. The insects can be released
outdoorsthough in winter they may die from cold unless they soon find
shelter. Another option is to do what Tedders does to keep the beetles he
harvests healthy until spring.

I keep them in containers in a refrigerator, he
says. Once a week I put the containers where the insects can warm up and
sip sugar water to keep from getting dehydrated. In spring, I release them when
aphids become available outdoors.

Entomologist Jeff Aldrich at ARS Insect Chemical Ecology
Laboratory in Beltsville, Maryland, is trying to learn whether the beetles
produce attractant chemicals, or pheromones, that trigger or regulate
aggregation. If so, he says, this could lead to a way to attract them to
suitable sites for collection or overwintering.

Aldrich uses gas chromatography with mass spectrometry to
examine the beetles chemical makeup. In aggregating ladybugs, we
are finding chemicals that may be pheromones, but we dont know if they
influence aggregation, he says. One thing we will have to do is
find out if these chemicals are missing from ladybugs that arent
aggregating.

Aggregation makes H. axyridis easy to collect for
research and redistribution. Since 1992 at Byron, the ladybugs have picked a
convenient sitean abandoned silo at ARS research farm. The silo, a
tube of light gray concrete, rises 31 feet, with a diameter of about 15 feet.

On warm, sunny afternoons in early November, the beetles walk on
and fly about the silos walls. Theyre attracted to the
silo, says Tedders, because it seems to offer shelter from the
coming winters cold. But since it really isnt
suitableit doesnt have a top to keep out rain, for
examplethey dont stick around long.

In 1993, scientists and technicians used soft brushes to
painstakingly sweep 17,500 lady beetles from the silo into containers.

When the lady beetles land on the wall, they tend to walk
upwards. This takes them to the apex of the vee, where they escape
through an openinginto a trap, a funnel leading into a container.

We collected more than 43,000 H. axyridis this way
in the fall of 1994, Tedders says.

Since 1993, university scientists have released Byrons
beetles to combat pecan aphids in California, New Mexico, and Texas.
These beetles may also have potential to control aphid pests of apple,
peach, and other fruit trees, Tedders says.By Jim De Quattro,
ARS.